In the polymerization of olefinic monomers having a terminal CH.sub.2 .dbd.C&lt; grouping with free radical catalysts, particularly those containing oxygen, it is generally necessary to stop the reaction after the polymerization has reached a predetermined state in order to obtain stable, uniform polymers. Also, in many polymerization systems, it is often desirable to stop the polymerization reaction short of complete conversion so that an effective agent of some kind must be employed to stop the reaction quickly without adversely affecting the polymerization product. The problem is particularly acute when employing the more active catalysts that give extremely fast polymerization rates and with, for example vinyl chloride polymers that are subject to thermal degradation.
In the manufacture of homopolymers and copolymers of olefinic monomers, and particularly from vinyl halides and vinylidene halides, one of the most important aspects is reaction control during the entire course of the polymerization. This is related, directly or indirectly, to such things as demands on heat exchange equipment, "run-away" reactions, formation of off-specification products, and the like. Accordingly, some means to terminate a polymerization, such as this, at any given time would be most desirable.
Heretofore, various shortstepping agents have been employed to terminate the polymerization of monoolefinically unsaturated monomers. However, many of these shortstopping agents do not work fast enough. Further, many of these shortstopping agents have been found to be ineffective in completely halting the polymerization or have been found to be effective only in such concentrations as result in discoloration of the polymer product. Therefore, there is a need for a shortstepping agent which overcomes the aforementioned difficulties.